1. Field of the Invention
The invention is related to the field of magnetic recording heads, and, in particular, to a magnetic recording head having a magnetoresistance (MR) read element with an extended stripe height, and having a shield with a shortened shield height as compared to the stripe height.
2. Statement of the Problem
Many computer systems use magnetic disk drives for mass storage of information. Magnetic disk drives typically include one or more magnetic recording heads (sometimes referred to as sliders) that include read elements and write elements. A suspension arm holds the recording head above a magnetic disk. When the magnetic disk rotates, an air flow generated by the rotation of the magnetic disk causes an air bearing surface (ABS) side of the recording head to ride a particular height above the magnetic disk. The height depends on the shape of the ABS. As the recording head rides on the air bearing, an actuator moves an actuator arm that is connected to the suspension arm to position the read element and the write element over selected tracks of the magnetic disk.
As the read element passes over the bits and bit transitions recorded on tracks of the magnetic disk, the magnetic fields for the bits and bit transitions modulate the resistance of the read element. The change in resistance of the read element is detected by passing a sense current through the read element, and then measuring the change in bias voltage across the read element. The resulting read back signal is used to recover the data encoded on the track of the magnetic disk.
The structure of a typical recording head includes a first shield, a read element formed on the first shield, two hard bias magnets formed on either side of the read element, and a second shield formed on the read element. The read element may comprise a Giant MR (GMR) read element, a Tunneling MR (TMR) read element, or another type of read element. If the recording head is being operated in a current perpendicular to the planes (CPP) fashion, then the first shield and the second shield are electrically connected to opposing surfaces of the read element to act as current leads for the sense current.
The read element in the recording head has a defined stripe height and track width. The stripe height comprises the distance between a back edge (which is the edge opposite the ABS) of the read element and the ABS. The stripe height and track width defines the resistance exhibited by the read element.
The first shield of the recording head has a shield height, which comprises the distance between a back edge (which is the edge opposite the ABS) of the first shield and the ABS. The shield height of the first shield is many times greater than the stripe height of the read element. For instance, a typical shield height may be 10, 20, or 30 microns, while a typical stripe height may be about 60 nanometers. The reason that the stripe height is constrained to a shorter height is that it forces the sense current that is applied through the read element to the region near the ABS of the read element. This region is where the flux from a recording transition on a magnetic disk is located allowing for improved readability of the bits on the magnetic disk.
One problem however with a read element having a shorter stripe height is that the read element is more susceptible to thermal magnetic resistance noise. Thermal magnetic resistance noise is inversely proportional to the volume of the read element. Thus, as the volume of the read element is lowered in order to force the sense current toward the ABS of the read element, the thermal magnetic resistance noise of the read element is increased. This unfortunately leads to a lower signal to noise ratio in the read element.